1. Preheat oven to 200°C. Grease a 22cm base measurement cake pan.
2. Heat oil in a large frying pan over medium heat. Cook onion for 3 minutes or until tender. Add coriander and cumin. Cook for 1 minute or until aromatic. Increase heat to high. Add mince, stirring constantly with a wooden spoon until browned. Stir in tomato paste and salsa. Bring to the boil. Reduce heat. Simmer for 15 minutes. Set aside to cool.
3. Place 1 tortilla in base of cake pan. Spoon one-third of cooled mince mixture over tortilla. Sprinkle one-third of cheese over mince, then one-third of spinach. Top with another tortilla. Repeat layers twice more, ending with a tortilla.
4. Bake for 20 minutes or until hot and top tortilla is golden. Rest for 10 minutes.
5. Place avocado and lemon juice into a bowl and mash with a fork.
6. Remove tortilla from pan. Place onto serving plate. Sprinkle with coriander leaves. Serve with avocado mixture.